Wednesday’s heat and humidity was not only suffocating, but also primed the atmosphere for explosive thunderstorms overnight. The storms that erupted between 11 p.m. and 2 a.m. became extremely powerful with damaging winds, frequent lightning, hail and even some flash flooding.

The fuel available to last night’s storms was nearly off-the-charts. The Convective Available Potential Energy or CAPE – a fancy way of measuring the energy available for thunderstorms – was in the 5,000-6,000 range – comparable to levels observed prior to the June 29, 2012 derecho.

Radar view 12:49 a.m. Thursday Radar view 12:49 a.m. Thursday

Fortunately, last night storm’s were not as widespread as the 2012 derecho. They were comprised of scattered individual thunderstorm cells and clusters, rather than a long, continuous line of storms. This is why some parts of the area experienced no rain and wind – the only evidence of the storms being distant, yet frequent lightning.

The areas hardest hit were just north and south of the District. North of town, the area from Frederick County (Md.) through Columbia to around Annapolis and Baltimore were hammered. South of town, Prince William County, southern Fairfax County (including Alexandria and Old Town), and southern Prince George’s County were worst impacted.

The winds

Some of the most extensive wind damage occurred around Alexandria, where multiple trees came down. This likely resulted from what’s known as a microburst – a downward burst or acceleration of violent winds that hit the ground and spread out in all directions. These winds have been to known to reach up to 100 mph.

Microburst diagram (National Weather Service)

Here are some pictures of the wind damage around Alexandria – with multiple downed trees reported in the Belle View area:

Here’s an image from a downed tree on an unfortunate home in Prince William County:

This storm produced a 62 mph gust at West Potomac High School in Alexandria. When it moved into southern Prince George’s County, Andrew’s Air Force Base clocked a gust of 78 mph.  The storm took down two large trees south of National Harbor, according to the National Weather Service.

Several reports of wind damage were logged by the National Weather Service for the cluster of storms that passed north of the District as well, around Baltimore and in Anne Arundel County, where winds were clocked up to 64 mph.

The lightning

The storm’s energy and vigorous vertical motions helped to ignite frequent lightning throughout the region.  Even areas that missed the rain could witness the amazing light show in the distance.  The flashes continued almost non-stop.

Lighting activity Thursday early morning, June 19, 2014 (D.C. Lightning Mapping Array) Lighting activity Thursday early morning, June 19, 2014 (D.C. Lightning Mapping Array)

D.C.’s Lightning Mapping Array shows the intense concentration of lighting where the storms came through (to the right). Over 30,000 customers lost power in the region (from the lightning and/or downed trees). Here are some lightning photos captured by readers:

Lightning over Washington Channel (Jason Kopp via Facebook)

Lightning from Annapolis (Jennifer Casey Photography via Facebook)

Lightning from Cleveland Park (Ian Livingston)

Lightning from Cleveland Park (Ian Livingston)


Flash flooding

Baltimore was hit by not only one storm, but a cluster of storms that cycled through the area. It thus received several waves of torrential rain that resulted in some flash flooding, and required water rescues for stranded vehicles. Doppler radar estimated over 3 inches of rain fell around Baltimore. The image showing the estimated amounts below does a nice job portraying the storm tracks and the rain hole over D.C. (aka the D.C. split):

Doppler estimated rainfall last 24 hours (National Weather Service)


The storms produced some small, mostly pea-sized, hail. A picture here:

Storms today?

Showers and thunderstorms are possible once again over the area today. But due to the activity that came through last night, the atmosphere is a bit worked over and won’t have the same available energy for storms that come through. (Stay tuned for further updates, as needed, on today’s storms)